Structural setting and tectonic evolution of the northern Hammam Faraun Block (Wadi Wasit-Wadi Wardan area), eastern side of the Suez rift

Abstract

The Wadi Wasit-Wadi Wardan area (northern part of the Hammam Faraun Block) lies on the eastern `side of the Suez rift between oppositely tilted half grabens. Detailed field mapping of the block indicates that the pre-rift and syn-rift rocks are deformed by N- to WNW-oriented normal faults and subordinate folds related mainly to the movement on nearby faults. The block can be divided structurally into three NNW oriented sub-blocks, the middle one of which is a large graben whereas the eastern one defines a rollover on the downthrown side of the listric rift-bounding fault. Seven deformations affected the Hammam Faraun Block, the earliest of which (D1, Early Eocene) was associated with pre-rift "Syrian arc" folding. Oligocene deformation (D2) affected the southernmost part of the block and is probably related to local uplift at the late stages of "Syrian arc" deformation. Early opening in the Suez rift (D3) was associated with basaltic volcanicity conformable with the underlying pre-rift rocks. Deformations D4 through D6 are directly related to continued opening and evolution of this rift. D4 event is related to the change from slow to rapid subsidence. A mid-rift (Mid-clysmic) event (D5) led to structural reorganization of the rift associated with uplift of the rift shoulder and deposition of fan conglomerates at the footslopes of fault scarps. Mild, late rift faulting marks the D6 event. Quaternary movements of local nature (D7) formed minor normal faults and are probably related to local, non-tectonic, readjustment above subsurface faults. The tectonic events of the Hammam Faraun Block indicate the transition from "Syrian arc" folding (related to the convergence between Africa and Eurasia due to the closure of the Neotethys) to the early stages of crustal separation between Africa and Arabia (leading to the opening of the Suez and ancestral Red Sea rifts). The onset of rifting is marked by a phase of Early Miocene volcanicity. Rift tilting followed this volcanicity and is related to the displacement on the listric normal faults at the rift boundary. Half grabens of the rift are marked by major, conjugate, steeply dipping breakaway faults at both sides. A listric fault marks one side and a planar fault marks the other side of each half graben. The northern part of the Hammam Faraun Block lies in the transfer zone between the northern and central half grabens of the Suez rift. It has a broad anticlinal structure being a "twist zone" or an overlapping convergent conjugate transfer zone between the listric normal faults of these two half grabens.